Separation and purification of fatty alcohols



United States Patent 3,028,435 SEPARATION AND PURIFICATION OF FATTYALCOHOLS Anthony L. Andrikides, Philadelphia, Pa., assignor t NorcoProducts Co., Inc., Philadelphia, Pa., a corporation of Pennsylvania NoDrawing. Filed May 8, 1959, Ser. No. 811,810

1 Claim. (Cl. 260-643) This is a continuation-in-part of my co-pendingapplication for separation and purification of fatty acids andglycerides,- filed March 19, 1959, Ser. No. 800,404.

This invention relates to the separation and purification of fattyalcohols. More particularly, it relates to the recovery, separation, andrefining of saturated fatty alcohols and unsaturated fatty alcohols frommixtures containing both saturated and unsaturated fatty alcohols.

A very important feature of this invention resides in the use of aparticular solvent selected from a particular group of solvents toseparate and/or purify the desired products, which solvent may be usedwithin moderate temperature ranges. These temperature ranges comprisehighs which may be characterized as warm, and those which may becharacterized as room temperature. The exact temperatures involved areof course more particularly pointed out below, but this generaldescription indicates one value of the invention, in eliminating thenecessity of extreme temperatures.

Many fatty alcohols, both saturated and unsaturated, are well known inthe art, and it is not necessary to exhaustively list here the manyknown fatty alcohols, nor to set forth their various sources. Inaddition, the uses and importance of fatty alcohols are well known inthe art, and it is not deemed necessary to set those forth herein.

It is an object of this invention to separate, refine, and purifysaturated fatty alcohols from mixtures containing saturated andunsaturated fatty alcohols.

It is an object of this invention to separate, purify, and refineunsaturated fatty alcohols from mixtures containing saturated andunsaturated fatty alcohols.

It is another object of this invention to recover, separate, and purifyfatty alcohols by means of differential solution in a particular solventselected from a group of solvents.

It is another object of this invention to separate, refine, and purifyfatty alcohols, by a solvent process, minimizing the temperature rangesrequired, the amount of solvent required, the cost of the process, andresulting in quantitative separations.

A still further object of this invention is to separate a mixture ofsaturated and unsaturated fatty alcohols into fractions which arerespectively relatively rich in solid or high melting-point componentsand respectively relatively rich in liquid or low melting-pointcomponents.

Other aims and objects of this invention are made apparent in thefollowing disclosure and claim.

The most important aspect and feature of this invention depends on theprocess of utilizing the differing solubility of the materials to beseparated, as set forth above, in a solvent selected from the groupconsisting of nitrated members of the methane (parafiin) series, whosegeneral formula is C H NO- and isomers thereof. Of this group thepreferred members are those in which n equals 4 or less, that is,nitro-methane, nitroethane, nitro-propane, and nitro-butane. Forexample, suitable solvents include l-nitropropane,

CH CH CH NO and the isomer 2-nitropropane, (CH CHNO highly soluble atroom temperatures, while the saturated fatty acohols are completely,substantially completely, or very highy insoluble at room temperatures.

The solvents recited above are individually referred to herein assolvent or nitrated parafiin series solvent.

In general, the method of this invention comprises dissolving saturatedfatty alcohols mixed with unsaturated fatty alcohols, in warm solventand then cooling to room temperature while stirring constantly. Thesaturates then crystallize out in easily filterable form. The mixture isfiltered. The filter cake containing the saturates are then washedoutwith the same solvent, and the residual solvent is recovered by theusual methods, as set forth below.

The filtrate, containing the unsaturated fractions, is then distilledunder vacuum to recover the solvent by usual methods. The filter cakemay be rid of the solvent by distillation under vacuum, or by steamdistillation.

The exact temperatures involved in the practice of this method are notdeemed quantitatively essential to the invention, but it is observedthat the warm or higher temperature is approximately 50 degrees C. orhigher. The room temperature or lower temperature is generally betweenapproximately 12 and 16 degrees C.

It is found that to obtain satisfactory commercial saturated fattyalcohol fractions from the mixture, it is necessary to subject thefilter cake of saturates to an additional throughput. That is, thefilter cake obtained as described above is redissolved andrecrystallized and filtered again. The filter cake obtained from thissecond throughput is the commercial product. The filtrates obtained fromeach of the two throughputs constitute commercially satisfactoryproducts. It is of course desirable that the minimum amount of solventbe used in the process. It has been found that a ratio of 4 parts ofsolvent to 1 part of mixed saturated and unsaturated fatty alcohols is asatisfactory and preferred approximate ratio. Obviously, greater ratiosof solvent may be used in the process. The exact preferred ratio setforth herein is not to be considered a necessary element of theinvention in itself. Depending on the material to be processed, it isapparent that the ratio of solvent may be reduced somewhat from thepreferred ratio, and as a matter of fact the exact ratio used is notcritical. As less solvent is used, below the ratio set forth aspreferred, the feasible practice of the process, becomes much moredifficult.

The practice of this method is made clearer by con sideration of thefollowing example.

Example I A sample Was provided of a mixture of fractions of saturatedfatty alcohols and unsaturated fatty alcohols, said mixture having beenobtained from sperm oil. The sample had an acid value of 1.5. It had asaponification value of three. It had an iodine value of 51-55, and wasmainly cetyl alcohol and oleyl alcohol.

One part of the mixture was mixed with four parts of nitropropane, andwas warmed. The fractions dissolved. The mixed solvent and fattyalcohols were then cooled while being stirred, to approximately 12degrees C., at which point crystallization of the saturated fractionsoccurred. The mixed solvent and fractions was then filtered.

The filter cake, comprising mainly saturates, was redissolved in thesame solvent, in the same ratio; that is, one part material to betreated, 4 parts solvent, and warmed. The mixture of solvent andmaterial to be treated was then cooled again to approximately 12 degreesC., during constant stirring, at which point recrystallization hadoccurred. The filter step was again applied.

The filtrates resulting from each of the two recrystallization stepswere combined. The solvent which was admixed with the filtrate wasremoved by vacuum distillation, and the solvent admixed with the filtercake was also removed by vacuum distillation.

The liquid fraction, or filtrate (after removal of sol vent) had asaponification value of 2, and an iodine value of 82. This fractioncomprised mainly oleyl alcohol.

The solid fraction (after removal of solvent) showed a saponificationvalue of 0, and an iodine value of 2.8. This fraction comprised mainlycetyl alcohol.

It is understood that additional repeated throughputs may be performed,resulting in still higher degrees'of separation or purification.

In this specification, the terms, separation, purification, andrefining, are loosely used in an interchangeable and equivalent manner.In common usage, the terms purification and refining would refer to theremoval of relatively minor portions of undesirable material from thematerial treated, but it is apparent that such processes are merely oneform of the broader process of separation.

The example cited above is merely illustrative of many performedexperiments. The same process as set forth in the example was carriedout using others of the named solvents and their isomers with equivalentresults. It has been found that homologues of the nitrated paraflin(methane) series above nitrobutane are not as satisfactory for use inthe process, althoughthe same differential solvent eifect is present.Also, the homologues above nitrobutane are much more difficult to obtaincommercially.

A characteristic of this group of solvents which makes them remarkably'apt for this process is that the solubility of saturates in them atroom temperature is almost nil. This makes for very high degrees ofseparation or purification, which may be characterized as quantitative.

Otli'e'r known sol've'nts are miscible with "water, tending toazeotropism. The recoveryof such solvents from the water is'di'flic'ult.The solvents of this invention are partially azeotropic, but are notmiscible with water. The solvents of this invention entirely dissolvethe material to be treated at slightly elevated temperatures, yetprovide quantitative separation at room temperatures. The lack of thenecessity of refrigeration below room tem perature is important.

Another advantage of the process of this invention is that the crystalsobtained in the filter cake are much better than those obtained by otherprocesses for ease in filtering. The need for filter aids may often beeliminated in the practice of this invention.

The scope of this invention is to be determined by the appended claim,and is not to be limited by the specific examples and description above,which are intended to be exemplary and not limiting.

I claim:

The separation of a mixture comprising mainly cetyl alcohol and oleylalcohol comprising dissolving one part of said mixture warm inapproximately four 'parts of a solvent consisting of one of the nitratedmembers of the methane series of hydrocarbons having the general formulaC H NO wherein n 'is an integer from 1 to 4, cooling to approximately 12degrees C. while constantly stirring, and filtering out crystallizedsolid matter, mainly cetyl alcohol, whereby the original said mixture isseparated into saturated and unsaturatedfractions.

References'Cited in the file of this patent UNITED STATES 'rAT'ENrs1,814,654 YOutZ July '14, 1931 2,081,721 Van Dijck et al May 25,19372,325,783 Lorand Aug. 3, 1943 OTHER REFERENCES Hodgman: Handbook ofChemistry and Physics (32 ed.) 1950, pages 814-815.

McElvain: The Characterization of Organic Compounds (rev. ed.) 1953,page 53.

Huntress et-*al.: Identification of Pure Organic Compounds, order 1,page 456, 4th printing,"September 1953.

